Multiple Sclerosis (MS) can be associated to many psychological symptoms. One of the most relevant is the experience of distress related to the disease, that can lead to the development of Post Traumatic Stress Disorder (PTSD). As far as we know there are no studies on the efficacy of psychological treatments in MS in spite of its relevance for patients' quality of life. Primary aim is to evaluate the efficacy of the treatment with Eyes Movement Desensitization and Reprocessing(EMDR) in PTSD secondary to MS. EMDR is the elective treatment (together with Cognitive Behavioural Therapy) for PTSD according to international guidelines. The secondary aims are to evaluate the efficacy of EMDR on the PTSD-associated symptoms of anxiety and depression and Quality of Life. The study design is a randomized clinical trial. Sixty patients with MS and PTSD will be pre-screened by using the IES-R and the Clinician Administered PTSD Scale. The patients will be randomized in two groups (30 in the experimental group and 30 in the control group).The psychological assessment will be performed in both groups with the same timing and tools: at baseline (T0), after treatment (T1) and 6 months later (T2) by two trained clinical psychologists (independent and blind to treatment) with the CAPS and the administration of self reports: Trauma Antecedent Questionnaire, Chicago Multiscale Depression Inventory, Hospital Anxiety and Depression Scale and Functional Assessment of Multiple Sclerosis. The experimental group will undergo 10 weekly sessions of 60 minutes each with EMDR following Shapiro's protocol for traumatic events. The efficacy will be evaluated comparing the results between T0, T1 and T2 and comparing the scores of the experimental and the control groups. Primary outcome measures will be: 1) the proportion of participants at T1 and T2 no longer meeting the Diagnostic and Statistical Manual (DSM IV-TR) diagnostic criteria for PTSD; 2) the reduction of CAPS scores for the four PTSD dimensions from pre-treatment to post-treatment evaluation and follow-up (avoidance, reexperiencing the traumatic event, hyperarousal and numbing). Secondary outcome measures will be: comparison of the scores of CMDI, HADS and FAMS of the two groups at T0, T1 and T2. The statistical procedure applied will be a repeated measures analysis of covariance both on the primary outcome continuous measures and on the secondary ones.